Since a magnetic thrust bearing using a superconducting coil can bear high thrust force, an application to a bearing of a large-scaled flywheel for storing energy, for example, is being made. In order to store the energy in the flywheel, a dynamotor is necessarily required to rotate the flywheel or to extract the rotating energy of the flywheel as electric energy.
Conventionally, the dynamotor is separately mounted from the magnetic thrust bearing using the superconducting coil and is operated with a rotation axis thereof being directly connected to a rotation axis of the flywheel.
In particular, with a flywheel for which rotation loss is necessarily reduced, a rotor is sometimes received in vacuum, so that it is difficult to adopt an equipment having heat generation to the rotor. Hence, it is difficult to use an inexpensive inductive type dynamotor having a simple structure and it is required to use a synchronous type dynamotor using a permanent magnet (for example, refer to Patent Literature 1).
Patent Literature 1: Japanese Unexamined Patent Publication No. 2001-343020